This invention relates generally to movements for timepieces using a crown to manually set the hands of the timepiece. More particularly, the invention relates to improved timesetting and a dual reduction gear assembly suitable for use in a three hand movement for a quartz analog wristwatch. Various constructions are known for setting the hands of wristwatches by pulling out a crown attached to a stem and manually rotating the stem, which is coupled to an internal gear engaging with the gear train to turn the hands. In a three hand wristwatch, in order to prevent the "seconds" hand from spinning too rapidly during timesetting, a common expedient is to provide means to arrest the motion of the "seconds" wheel and to include a slipping friction coupling somewhere in the gear train to permit only that portion of the gear train to turn which rotates the "minutes" hand and the "hours" hand. Such a friction coupling device permitting slipage during hand setting is seen in U.S. Pat. No. 3,487,633, issued Jan. 6, 1970 to P. Wuthrich. A three hand quartz analog movement generally employs a stepping motor to drive the "seconds" wheel, a wheel and pinion reduction gear assembly to drive the "minutes" wheel from the "seconds" wheel and another wheel and pinion reduction gear assembly to drive the "hours" wheel from the "minutes" wheel.
A three hand wristwatch movement is disclosed in U.S. Pat. No. 4,426,158, issued Jan. 17, 1984 to Mueller et al., which incorporates a stepping motor rotor having a two-pin pinion driving a seconds wheel and seconds spindle. Coaxially disposed around a post supporting the seconds spindle from the stepping motor stator are two rotatable sleeves with connected wheels, one for the minutes and the other for the hours. A pair of wheel and pinion reduction gear assemblies are coaxially mounted to rotate with respect to one another and with respect to the stationary bearing support. One such wheel and pinion reduces the speed to drive the minutes wheel. The other wheel and pinion is driven by a pinion on the minutes spindle and reduces speed further to drive the hours wheel. This construction requires a pair of coaxially mounted reduction gear assemblies which are continuously rotatable with respect to one another as well as with respect to the stationary bearing support.
The aforementioned Mueller Patent No. 4,426,158 employs a setting mechanism for the hands which causes a timesetting gear train engaged with one of the aforesaid wheel and pinion reduction gears to turn the hands, and requires engaging and disengaging one set of gears to set the time, a process which offers the possibility of breakage of teeth.
An improved three hand movement which eliminates one set of gears used in the aforesaid Mueller patent is disclosed in pending U.S. application Ser. No. 07/303,413 filed Jan. 30, 1989 in the name of H. Schwartz and P. Wuthrich and assigned to the present assignee. The improvement comprises a dual reduction gear assembly with a single shaft rotatably mounted in the frame having a toothed third wheel driven by the reduction drive pinion and having a first reduction pinion and second reduction pinion directly driving the hours and minutes wheels, respectively, from the same shaft. In the preferred embodiment, the rotor pinion, the reduction drive pinion, and first reduction pinion are of the two-pin type, while the second reduction pinion is an ordinary spur gear.
Accordingly, one object of the present invention is to provide an improved three hand timepiece movement which provides an improved timesetting mechanism and fewer parts.
Another object of the present invention is to provide an improved timesetting reduction gear for a three hand quartz analog wristwatch movement.